I have a 1993 4.0 ranger with the automatic it starts and drives just fine but when it gets hot or I drive through a puddle it starts to cut spark at 3k rpm then it moves down to 2.5k rpm. I have had the trans rebuilt and tried fixing this issue in a number of ways

 

Welcome to the forum

All engine computers have a REV Limiter set for 3,000rpm IF...........trans is in Park or Neutral
But since this only happens in specific conditions I doubt that's the issue

But could still be wiring issue for the REV Limiter
You have an A4LD automatic in a 1993 Ranger(1986-1994)
On the drivers side of the transmission above the shifter is the NSS(neutral safety switch), its a plunger type switch that screws in above the shifter and has 4 connection, can be 4 or 5 wires
If does Reverse lights with 2 connections
Other 2 are the Neutral "sensor", this allows you to activate starter motor only in Park or Neutral
Unplug this connector and check the wires for frayed ends or water intrusion that could short the wires together

Computer in a 1993 Ranger is in the engine bay, far drivers side, and down low, follow the larger wiring harness down the inner fender and you will see the 60 wire plug-in for the computer
Unplug it, its held in by a bolt on the center, inspect it for water intrusion
You can pull out the computer at this time, 2 more bolts, and open it up to look for water intrusion or circuit board issues, up to you
But there are 3 capacitors that will fail after 20 years and should be replaced with newer ones just as preventative maintenance easy to do it you or a friend can solder, under $5

1990-1994 4.0l uses an EDIS-6 module to run the spark system
It is located on the Rad support, usually drivers side, and can be on the side behind the grill or on the engine bay side of rad support
Looks like this: http://www.mkosonen.com/edis6module.jpg
Again look at the wires and connector for signs of water intrusion

Crank sensor
Its on the front of the engine next to the crank pulley at about 10:00 looking at front of engine, so easily splashed with water when driving
Its a 2 wires sensor with a shield wire
It "reads" a tone wheel(reluctor ring) which looks like a "gear", it has 35 teeth, 1 tooth ever 10deg then 1 missing tooth to ID top dead center for #1 cylinder
Crank sensor generates its own voltage, each time a tooth passes by it creates a voltage pulse, so very low voltage and easy to inhibit with a poor connection, or if mud gets in between teeth on tone ring

This is all assuming your description of a "spark" issue is the cause

 

Thanks for all the help I thought I saw I computer tucked into the firewall on the drivers side, but I thought there was no way it would be there. I found a hole that the previous owner had drilled in the wheel well liner which would explain how water could get on the computer. Thanks.